Remove irrelevant tests and unused testing attribute

Author: Nashenas88

src/libsyntax/feature_gate.rs

@@ -659,12 +659,6 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
                                            "rustc_attrs",
                                            "internal rustc attributes will never be stable",
                                            cfg_fn!(rustc_attrs))),
-    ("rustc_move_fragments", Normal, Gated(Stability::Unstable,
-                                           "rustc_attrs",
-                                           "the `#[rustc_move_fragments]` attribute \
-                                            is just used for rustc unit tests \
-                                            and will never be stable",
-                                           cfg_fn!(rustc_attrs))),
     ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
                                      "rustc_attrs",
                                      "the `#[rustc_mir]` attribute \

src/test/compile-fail/feature-gate-rustc-attrs.rs

@@ -14,7 +14,6 @@
 
 #[rustc_variance] //~ ERROR the `#[rustc_variance]` attribute is just used for rustc unit tests and will never be stable
 #[rustc_error] //~ ERROR the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
-#[rustc_move_fragments] //~ ERROR the `#[rustc_move_fragments]` attribute is just used for rustc unit tests and will never be stable
 #[rustc_foo]
 //~^ ERROR unless otherwise specified, attributes with the prefix `rustc_` are reserved for internal compiler diagnostics